Ultrafunk Reverb - low CPU, good presets, and has band window so you can limit effect to a wide or short band anywhere along the freq spectrum. I find that unless I can exclude bass from reverb effect, it can get too muddy there.

Works with impulses and comes with many created in actual environments from Civic Centers, theaters to small bathrooms and locker rooms, also mic models. You can create your own also. It's parameters are almost infinite.

I have tried many reverbs and I have found Ultrafunk's reverb to be, by far, the best one for lead vocals, and other instruments.
Also, Ultrafunk's delay and compressor effects are really good, better than any other ones I have tried, and believe me I have tried many.
It's a shame Ultrafunk is going out of business.

You folks should really check out my post on 'SIR' that's drifting off the first page. It's along the same lines as Acoustic Mirror, but gives you prints of THE classic reverb sounds. It's free. Although you can't tweak it like a plug-in verb, half the battle has been fought because of where the sound came from. My impressions are that it's going to be the future of this stuff (reverbs), because we're all chasing the 'big sounds' anyway, and no one has emulated the 'lexicon' sound w/ a soft verb. At least yet.....
CAA

I'll second the comments on the Ultrafunk reverb, but unfortunately it's not currently available (they've stopped sales indefinitely).

Two others (shareware) to consider are Silver Spike's ReverbIt, and Ambience by Smart Electronix. Ambience is quite nice and a new version with a snazzy-looking gui is due out any day now. The developers ask only for a $10 donation.

Sorry folks,
Not trying to be confusing--or even imply that I'm on the cutting edge (but I just might be). I picked this up on the UAD-1 forum. I don't want to start an argument, but the plugs w/ the UAD are better than anything I've ever heard (although they may color in a way people don't like). Anyway, many of the people on the forum are from Germany, so the tone or the forum is a bit different--definitely more geared toward production--and they are good! The songs I hear posted are typically a notch above what you get on most forums (present company excluded, of course).
When it came to arguing about reverb quality, and what is possible natively (UAD has a new one about to be released w/ much fanfare), this 'SIR' thing kept popping up. Since I just got a VST adapter, I decided to look further to examine how these people were getting duplicate results from high dollar outboard processing gear from within a native environment. The following is the best way I can barely explain it:
Someone w/ an Eventide Orville runs a test tone through a Hall Reverb algorithm. This creates a .wav file. They then (hocus pocus) remove the original tone, leaving only the print of the reverb qualities and tails. The 18 second limit is referring to the length of the tail recorded. This is the way that Acoustic Mirror operates, but it is done in actual environments. The only drawback to that is that we like the quality of artificial reverb (esp. us ambient types), as we've been hearing Lexicon, Yamaha, and TC 'verbs on recordings for years.
The plug-in is called 'SIR', and the .wav files you load are called 'impulses'. It is a VST plug available at the first link (I know the site's confusing) in the other post, and the impulses are available for download at the 'noisevault'. The current version only supports 16/44.1 .wavs, but there will soon be a 24 bit available. You can't manipulate parameters as you can a hardware unit, but there are enough available to shape your sound. It has high latency, and eats at the CPU, but I slapped it on one of my solo acoustic pieces, and lemme' tell ya'--that's the sound! Some of you w/ your beasts of processors could probably run a few instances of it in each project, or just apply destructively.
That's about the best I can do. Download 'SIR', download the 2 impulse examples on that page and see what you think. The only other thing I can think to tell you is that the impulses on noisevault are downloaded in .rar format. I have no idea what kind of zip file that is, but there was a trial version of something that unpacked all of them--and I downloaded ALL of them. This is your chance to say 'I've been using impulse reverbs since.....'
I'm interested to hear anyone's feedback. It sounds like it's supposed to--and better than any soft verb I've heard. Whether it's as functional is another story.....
CAA

Thanks GG. I did understand the concept, but since it wasn't a plugin I got fidgety when I got confused at the site. Well, onward through the fog.
I'll download 'it' and 'them' and I probably won't have enough time to report back tonight - but I'll post tomorrow. Thanks again.